1. Field of the Invention
The present invention relates to elastomeric connectors that are used to electrically interconnect contact areas on opposing surfaces by compressing the elastomeric connectors between the opposing surfaces. More specifically, the present invention relates to the structure of elastomeric connectors and the methods used to manufacture elastomeric connectors.
2. Prior Art Statement
As electronic circuitry becomes smaller and more densely populated with components, it is often difficult to interconnect separate electronic circuits using traditional soldering techniques. The difficulty of using solder is particularly evident when contact areas on opposing circuit boards must be joined. In the prior art, land grid arrays were commonly placed between opposing contact areas. The land grid arrays were then soldered in place to both contact areas. However, due to many variables, such as temperature stress, plating variations, substrate warpage and the like, such soldered connections often proved unreliable.
In an attempt to improve the reliability of connections between opposing contact surfaces, elastomeric connectors have been developed. Elastomeric connectors contain conductive elements that are suspended in an elastomeric substrate. The conductive elements are exposed on the top surface and bottom surface of the elastomeric substrate. When the elastomeric connector is placed between opposing contact points, the contact points contact the conductive elements that are contained within the elastomeric connector, thereby creating an electrical interconnection. The elastomeric material suspending the conductive elements allows the conductive elements to expand and contract as needed in between the opposing contact points without disrupting the electrical interconnection.
In the prior art, elastomeric connectors typically are manufactured by molding elastomeric material around conductive elements. The molded assembly is then often sliced into segments to expose the edges of the conductive elements within the elastomeric material. Such prior art elastomeric connectors are exemplified by U.S. Pat. No. 5,101,553 to Carey, entitled Method Of Making A Metal-On-Elastomer Pressure Contact Connector; and U.S. Pat. No. 4,520,562 to Sado, entitled Method For Manufacturing An Elastic Composite Body With Metal Wires Embedded Therein.
A problem associated with such prior art elastomeric connectors is that they are difficult and expensive to manufacture. The molding of elastomeric material around a dense grouping of conductive wires requires precise molding techniques, expensive molds and exacting premolding set-up tolerances. Furthermore, due to the pressures experienced during molding, ultra thin conductive wires typically are not used because the thin wires can move out of place or break during the molding procedure. Accordingly, using prior art manufacturing techniques, it is very difficult to produce an elastomeric connector with very thin conductive elements that embody a low impedance, a low inductance and a low surface resistance. Such characteristics, however, are required for many types of circuits. Accordingly, elastomeric connectors are not preferred in certain types of circuit designs.
The difficulty in molding elastomeric connectors also limits the shapes into which the elastomeric connectors can be molded. Typically, the shape capable of being produced in the prior art is a generally planar elastomeric connector having a flat top surface and a flat bottom surface. Accordingly, elastomeric connectors are typically not selected in a situation where unusually oriented contact points must be interconnected.
Another problem associated with prior art elastomeric connectors is when the elastomeric connector is compressed and released, the elastomeric material may expand to a degree greater than that of the conductive wires contained within the elastomeric material. As a result, the conductive wires become buried within the elastomeric material. Accordingly, when the elastomeric connector is again compressed, the elastomeric material may shield some of the conductive wires and make the elastomeric connector less conductive.
A need therefore exists in the prior art for an improved elastomeric connector that embodies both a low impedance and a low inductance. The need also exists for an elastomeric connector that can be configured in unusual shapes and can be repeatedly compressed without loss of conductivity due to buried conductive elements.
These needs are met by the present invention as described and claimed below.
The present invention is an improved elastomeric connector and the associated method used to manufacture the elastomeric connector. The elastomeric connector includes a segment of a dielectric substrate having a top surface and a bottom surface. A plurality of conductive elements are advanced through the dielectric substrate in a predetermined pattern. Portions of the conductive elements lay exposed on the top surface and the bottom surface of the dielectric substrate within the selected pattern. Accordingly, any contacts that abut against the top surface and the bottom surface of the elastomeric connector will be electrically interconnected by the conductive elements. Each of the conductive elements is configured in a manner that prevents the dielectric substrate from enveloping the conductive elements at the points where they enter the dielectric substrate. Accordingly, as the dielectric substrate is repeatedly compressed, the conductive elements resist becoming buried within the material of the dielectric substrate.
The material of the conductive elements, size of the conductive elements and pattern for the conductive elements can be selectively altered to match the elastomeric connector to a desired impedance value. Furthermore, the pattern of the conductive elements can be custom designed for a given application, thereby producing a perfectly matched elastomeric connector for a given application.